The glaucoma drainage device of the present invention pertains to devices useful in the treatment of recipients having glaucoma. More particularly, the present invention pertains to a glaucoma drainage device that is implanted in the eye of a recipient that minimizes the size of the incision required to implant the device.
Glaucoma is a condition in which the optic nerve is damaged. The optic nerve is damaged due to excessively high intraocular pressure in the eye. Excessive pressure occurs when the aqueous humor, the clear liquid in the eye, does not properly drain from the eye. Regardless of the reasons why the intraocular pressure builds in the eye, if left untreated the excessive intraocular pressure will likely damage the optic nerve and cause irreversible loss of eyesight.
A method of treating glaucoma when other less invasive methods of treatment such as drugs do not relieve the excessive intraocular pressures in glaucoma patients is incisional filtration implant surgery. In this type of surgery a tube is inserted through an incision, a sclerostomy, in the sclera of the recipient""s eye. The purpose of implanting the drainage tube is to provide a means for the aqueous humor to drain from the eye and thus alleviate the excessive intraocular pressures. The filtration surgery may involve implanting a drainage tube connected to a plate that acts a reservoir that is drained via the drainage tube. A problem associated with implanting conventional glaucoma drainage devices comprising a plate and a tube is the incision required to deliver the device to the implant site. The more extensive the surgery incision required to implant the device the greater the risks of postoperative infection, inflammation and length of healing time of the surgery implant site.
The glaucoma drainage device of the present invention comprises a episcleral plate, foldable and rollable upon itself, and a drainage tube connected to the foldable and rollable plate at one end and free at the other end that may be implanted in a recipient""s eye through an injection delivery system for drainage of aqueous humor for the treatment of glaucoma. The present invention may further comprise a peripheral ridge along the upper surface of the episcleral plate to add volume to the plate for improved drainage; retention rings and bands for maintaining the glaucoma drainage device at its intended and implanted location; and a terminal collar located at or near the free end of the drainage tube for preventing migration of the device into the cornea of the recipient.
The present invention will provide an effective treatment for glaucoma by improving postoperative filtration and successful reduction of intraocular pressure. Additionally, the common risks associated with glaucoma incisional surgery to reduce the intraocular pressure in glaucoma patients such as postoperative infection, inflammation and the length of surgery site healing time are all believed to be reduced due to the single injection stab incision associated with the present invention as compared to traditional glaucoma incisional surgery using traditional glaucoma drainage devices requiring more extensive incisions. The device of the present invention is capable of being rolled and folded upon itself so that the entirety of the device may be delivered to the implant site via an injection delivery system such as a needle. The episcleral plate itself is sized and shaped to fit on a recipient""s eye to provide adequate filtering and drainage and yet the entire invention is capable of being delivered to the implant site via an injection delivery system.
The episcleral plate may be constructed of silicone or other bio-compatible materials that have proven to be well suited for glaucoma drainage devices. Furthermore, in order to effectuate the rolling and folding capabilities of the present invention so that the required incision in the sclera, a sclerostomy, is optimally minimized to an needle injection-sized incision the episcleral plate may be constructed of a material having a memory of its unfolded shape. The memory of the plate material will work to resist permanent deformity of the plate as a result of folding and rolling the plate upon itself for implantation and also work to ensure the plate returns to its intended shape for a proper fit in the recipient""s eye. Special folding techniques may also be used to ensure minimizing deformation of the device. Still other embodiments may have resilient or inflatable veins appropriately disposed in the device so that the device can open to its desired shape once implanted in the recipient""s eye.
Other beneficial and useful aspects of the present invention include having an inflatable rim. An embodiment of the present invention having an inflatable rim may be folded and rolled upon itself with the rim in a non-inflated or deflated state for ease of delivery to the implant site. After insertion into a recipient""s eye at the desired location, the inflatable rim of the present invention may be inflated to provide a ridged wall to add volume to the glaucoma drainage device for better filtration. The rim may be inflated with air, B.S.S. or other fluids.
The drainage tube of the present device may be a tube with a passageway therethrough for drainage of aqueous humor from the episcleral plate located and implanted on top of the sclera through an sclerostomy to the anterior chamber. The tube may also incorporate pressure regulation capabilities such as valves whereby aqueous humor is allowed to drain through the drainage tube when the intraocular pressure exceeds a predetermined threshold pressure. The drainage tube may further comprise a passageway for drainage of aqueous humor and a passageway for inflating the inflatable rim of embodiments having an inflatable rim. The combined aqueous humor drainage tube and inflation tube may, individually or in combination, be enveloped in a drainage tube sleeve like other embodiments solely having an aqueous drainage tube.
In order to avoid the post operative complication of hypotony due to over filtration, the free end of the aqueous shunting tube implanted in the anterior chamber may be covered with a water impermeable, pigmented membrane. This membrane can either be manually opened with a sharp instrument or melted open with an ophthalmic laser to allow the free egress of aqueous humor from the anterior chamber when deemed appropriate by the surgeon.
The drainage tube of the device may also have bands, rings or other retention structures affixed thereto for retaining the drainage tube and the implanted device in the desired location. The retention bands, rings or other structures may be sized and configured to prevent and aid in preventing leakage around the drainage tube. The device may also include a terminal collar. The terminal collar is typically located at or near the end of the drainage tube not connected to the episcleral plate.
Another benefit of the present invention is that the device may also be implanted by rolling and folding the device and then feeding the rolled and folded device along a guide wire into the sub-tenon""s space of the recipient""s eye. As with the implantation technique involving passing the rolled and folded device through the lumen of a cannula or needle, the device is delivered to the implant site on the recipient""s sclera while the free end of the tube is in place by the terminal collar and/or retention bands to prevent the tube from migrating into the cornea of the recipient.
In addition to the above descriptions and benefits, it is important to realize that the present invention may be implanted using conventional and traditional techniques. The advantage gained is that the conjunctival incision made to accommodate the device can be made much smaller.